This is a study designed to compare the agreement of hemoglobin (Hb) measurements, documented at specific time points (the time a blood sample was obtained by the standard clinical care after physician/nurse orders it and, during that same time, the Hb value recorded by the Masimo Radical-7 monitor); recorded several times throughout patient's major spine surgery procedure (depending on how many times the physician/nurse orders the Hb value to be tested), between the standard clinical practice {intermittent measure of Hb [Cedar Sinai Medical Center (CSMC) Lab and outside lab) and Masimo radical-7 device (continuous, non-invasive Hb level measurements)*.